Often times, it is desirable to evenly distribute light around an area. This may be to avoid shadows or to give the area a consistent appearance. Where energy consumption is not a concern, this can usually be achieved by using a sufficiently large number of illumination sources. Where energy consumption is a concern, for instance if the system is operating on battery power, it is not possible to simply throw more light at the problem. Furthermore, with a limited number of light sources, illuminating the area becomes even more challenging where the area contains opaque obstacles that block an illumination source from illuminating the entire area. Because of these problems, it would be beneficial to have a system and techniques for evenly lighting an area with a small number of light sources.
Various lighting techniques utilizing light pipes are known. Generally, a light pipe is a cavity (frequently rectangular, cylindrical, or some other simple geometric shape) that transports light to another location while minimizing the loss of light during transport, such as by absorption into the walls of the light pipe. These known techniques may not be applied wholesale to the lighting of the perimeter of a substantially cylindrical area.
When the area to be illuminated is substantially cylindrical other considerations come into play. Using the cylinder itself as a light pipe does not work for many materials because those materials absorb too much light. Adding highly reflective paint to the surface of the material also is disfavored because even that paint still absorbs too much light. Guiding light through a separate inner tube produces results closer to those desired, but sufficient uniformity of light distribution is achieved only when there is a sufficiently long lead up into the desired scattering area, so the technique does not work well in shorter cylinders.